In a conventional graphics display system, an image register is often provided for the processing of information associated with the displayed image, particularly information associated with each pixel of the image. In particular, a color code may be associated with each pixel (i.e., each pixel in a graphics image may have a plurality of colors). Further, a common processing task assigned to such image registers is that of "mixing" colors associated with a particular pixel in order to produce an image, for example, when mixing layers of an image. Thus, when modifying an image on a graphics display through the above-mentioned color "mixing" function, a system for controlling the displayed image must ensure that the data stored in a memory associated with the image register is modified only in accordance with a predefined color mixing function.
This modification process conventionally requires two steps per pixel: a first step to read the image data, particularly the color code, from the image register memory, and a second step to process this retrieved image data in accordance with the predefined color mixing function, and writing the processed image data, including the modified color code, into the image register memory. Conventionally, the predefined function entails addition of the pre-existing color code and the color code to which it is to be mixed. As can be appreciated, the conventional graphics arrangement requires a complicated two-step process for each image pixel, including a "wait" state for retrieving the stored image data prior to mixing. The sequential method of processing employed in conventional color mixing image registers limits the execution speed, and accordingly, limits the speed at which the system can display a modified "color mixed" graphics image.
It is therefore an object of the present invention to provide an image register for use in a color mixing device that minimizes or eliminates the shortcomings of the prior art image registers.
It is another object of the present invention to provide a color mixing device by using a high speed image register.
It is a further object of the present invention to provide a color mixing device by using a high speed image register that can improve significantly the execution speed of the color mixing process.
It is another object of the present invention to provide a color mixing device by using a high speed image register that utilizes two individual static random access memory (SRAM) devices for storing image data.
It is still another object of the present invention to provide a color mixing device by using a high speed image register that can simultaneously color mix image data corresponding to address n while reading image data corresponding to address n+1 in advance of its need for mixing such that the stored image data associated with address n+1 is immediately available for processing in a next subsequent cycle to thereby eliminate a "wait" state during the color mixing calculation.